.TH std::ranges::destroy_n 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::ranges::destroy_n \- std::ranges::destroy_n

.SH Synopsis
   Defined in header <memory>
   Call signature
   template< no-throw-input-iterator I >

       requires std::destructible<std::iter_value_t<I>>                   \fI(since C++20)\fP

   constexpr I destroy_n( I first, std::iter_difference_t<I> n )
   noexcept;

   Destroys the n objects in the range starting at first, equivalent to

 return std::ranges::destroy(std::counted_iterator(first, n), std::default_sentinel).base();

   The function-like entities described on this page are niebloids, that is:

     * Explicit template argument lists cannot be specified when calling any of them.
     * None of them are visible to argument-dependent lookup.
     * When any of them are found by normal unqualified lookup as the name to the left
       of the function-call operator, argument-dependent lookup is inhibited.

   In practice, they may be implemented as function objects, or with special compiler
   extensions.

.SH Parameters

   first - the beginning of the range of elements to destroy
   n     - the number of elements to destroy

.SH Return value

   The end of the range of objects that has been destroyed.

.SH Complexity

   Linear in n.

.SH Possible implementation

   struct destroy_n_fn
   {
       template<no-throw-input-iterator I>
           requires std::destructible<std::iter_value_t<I>>
       constexpr I operator()(I first, std::iter_difference_t<I> n) const noexcept
       {
           for (; n != 0; (void)++first, --n)
               std::ranges::destroy_at(std::addressof(*first));
           return first;
       }
   };

   inline constexpr destroy_n_fn destroy_n{};

.SH Example

   The following example demonstrates how to use ranges::destroy_n to destroy a
   contiguous sequence of elements.


// Run this code

 #include <iostream>
 #include <memory>
 #include <new>

 struct Tracer
 {
     int value;
     ~Tracer() { std::cout << value << " destructed\\n"; }
 };

 int main()
 {
     alignas(Tracer) unsigned char buffer[sizeof(Tracer) * 8];

     for (int i = 0; i < 8; ++i)
         new(buffer + sizeof(Tracer) * i) Tracer{i}; //manually construct objects

     auto ptr = std::launder(reinterpret_cast<Tracer*>(buffer));

     std::ranges::destroy_n(ptr, 8);
 }

.SH Output:

 0 destructed
 1 destructed
 2 destructed
 3 destructed
 4 destructed
 5 destructed
 6 destructed
 7 destructed

.SH See also

   ranges::destroy_at destroys an object at a given address
   (C++20)            (niebloid)
   ranges::destroy    destroys a range of objects
   (C++20)            (niebloid)
   destroy_n          destroys a number of objects in a range
   \fI(C++17)\fP            \fI(function template)\fP
